[gcc r14-234] RISC-V: Add auto-vectorization compile option for RVV

[Jeff Law <law@gcc.gnu.org>]

https://gcc.gnu.org/g:2fb7df82b8edd64ea31417592619c4cee00b05bc

commit r14-234-g2fb7df82b8edd64ea31417592619c4cee00b05bc
Author: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
Date:   Tue Apr 25 21:05:54 2023 -0600

    RISC-V: Add auto-vectorization compile option for RVV
    
    This patch is adding 2 compile option for RVV auto-vectorization.
    1. -param=riscv-autovec-preference=
       This option is to specify the auto-vectorization approach for RVV.
       Currently, we only support scalable and fixed-vlmax.
    
        - scalable means VLA auto-vectorization. The vector-length to compiler is
          unknown and runtime invariant. Such approach can allow us compile the code
          run on any vector-length RVV CPU.
    
        - fixed-vlmax means the compile known the RVV CPU vector-length, compile option
          in fixed-length VLS auto-vectorization. Meaning if we specify vector-length=512.
          The execution file can only run on vector-length = 512 RVV CPU.
    
        - TODO: we may need to support min-length VLS auto-vectorization, means the execution
          file can run on larger length RVV CPU.
    2. -param=riscv-autovec-lmul=
       Specify LMUL choosing for RVV auto-vectorization.
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-opts.h (enum riscv_autovec_preference_enum): Add enum for
            auto-vectorization preference.
            (enum riscv_autovec_lmul_enum): Add enum for choosing LMUL of RVV
            auto-vectorization.
            * config/riscv/riscv.opt: Add compile option for RVV auto-vectorization.

Diff:
---
 gcc/config/riscv/riscv-opts.h | 15 +++++++++++++++
 gcc/config/riscv/riscv.opt    | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/gcc/config/riscv/riscv-opts.h b/gcc/config/riscv/riscv-opts.h
index cf0cd669be4..4207db240ea 100644
--- a/gcc/config/riscv/riscv-opts.h
+++ b/gcc/config/riscv/riscv-opts.h
@@ -67,6 +67,21 @@ enum stack_protector_guard {
   SSP_GLOBAL			/* global canary */
 };
 
+/* RISC-V auto-vectorization preference.  */
+enum riscv_autovec_preference_enum {
+  NO_AUTOVEC,
+  RVV_SCALABLE,
+  RVV_FIXED_VLMAX
+};
+
+/* RISC-V auto-vectorization RVV LMUL.  */
+enum riscv_autovec_lmul_enum {
+  RVV_M1 = 1,
+  RVV_M2 = 2,
+  RVV_M4 = 4,
+  RVV_M8 = 8
+};
+
 #define MASK_ZICSR    (1 << 0)
 #define MASK_ZIFENCEI (1 << 1)
 
diff --git a/gcc/config/riscv/riscv.opt b/gcc/config/riscv/riscv.opt
index ff1dd4ddd4f..ef1bdfcfe28 100644
--- a/gcc/config/riscv/riscv.opt
+++ b/gcc/config/riscv/riscv.opt
@@ -254,3 +254,40 @@ Enum(isa_spec_class) String(20191213) Value(ISA_SPEC_CLASS_20191213)
 misa-spec=
 Target RejectNegative Joined Enum(isa_spec_class) Var(riscv_isa_spec) Init(TARGET_DEFAULT_ISA_SPEC)
 Set the version of RISC-V ISA spec.
+
+Enum
+Name(riscv_autovec_preference) Type(enum riscv_autovec_preference_enum)
+The RISC-V auto-vectorization preference:
+
+EnumValue
+Enum(riscv_autovec_preference) String(none) Value(NO_AUTOVEC)
+
+EnumValue
+Enum(riscv_autovec_preference) String(scalable) Value(RVV_SCALABLE)
+
+EnumValue
+Enum(riscv_autovec_preference) String(fixed-vlmax) Value(RVV_FIXED_VLMAX)
+
+-param=riscv-autovec-preference=
+Target RejectNegative Joined Enum(riscv_autovec_preference) Var(riscv_autovec_preference) Init(NO_AUTOVEC)
+-param=riscv-autovec-preference=<string>	Set the preference of auto-vectorization in the RISC-V port.
+
+Enum
+Name(riscv_autovec_lmul) Type(enum riscv_autovec_lmul_enum)
+The RVV possible LMUL:
+
+EnumValue
+Enum(riscv_autovec_lmul) String(m1) Value(RVV_M1)
+
+EnumValue
+Enum(riscv_autovec_lmul) String(m2) Value(RVV_M2)
+
+EnumValue
+Enum(riscv_autovec_lmul) String(m4) Value(RVV_M4)
+
+EnumValue
+Enum(riscv_autovec_lmul) String(m8) Value(RVV_M8)
+
+-param=riscv-autovec-lmul=
+Target RejectNegative Joined Enum(riscv_autovec_lmul) Var(riscv_autovec_lmul) Init(RVV_M1)
+-param=riscv-autovec-lmul=<string>	Set the RVV LMUL of auto-vectorization in the RISC-V port.